Artículos SCI
2008
2008
Reactividad de Sólidos
Syntesis by reactive grinding of molibdenum iron bimetallic nitride
Roldan, MA; Ortega, A; Palencia, I; Real, CRevista de Metalurgia, 44 (2008) 13-18
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The transition metal nitride ternary show similar properties to the binary nitride and some times this behaviour are improved. In the present work, the molybdenum-iron nitride has been prepared by reactive grinding from the two metals under nitrogen atmosphere at a pressure of 11 bar. The characterization of the compound is presented and it is also shown a study of the stability of the nitride under several atmospheres.
Enero, 2008 | DOI:
Materiales Ópticos Multifuncionales
Spectral Response of Opal-Based Dye-Sensitized Solar Cells
Mihi, A.; Calvo, M. E.; Anta, J. A.; Miguez, H.Journal of Physical Chemistry C, 112 (2008) 13-17
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Herein we present an experimental study of the spectral dependence of the photogenerated current of opal-based solar cells. We analyze the incident photon-to-current conversion efficiency (IPCE) for dye-sensitized solar cells in which colloidal crystals are introduced in different configurations. We prove that a dye-sensitized nanocrystalline titanium oxide electrode moulded in the shape of an inverse opal shows a decrease of efficiency for the spectral region in which a photonic stop band opens up. Contrarily, when a standard thin film of disordered titania nanocrystallites is coupled to an inverse opal, the mirror effect of the photonic crystal at band gap frequencies increases the light harvesting efficiency of the cell and thus the IPCE. This effect is further demonstrated by coupling an inverse opal multilayer to a homogeneous electrode, with two well-defined spectral ranges of increased photogenerated current being detected.
Enero, 2008 | DOI: 10.1021/jp7105633
Materiales Nanoestructurados y Microestructura
Permanent magnetism in thiol capped nanoparticles, gold and ZnO
Crespo, P.; Garcia, M. A.; Fernandez-Pinel, E.; De la Venta, J.; Merino, J. M.; Quesada, A.; Hernando, A.; Fernandez, A.; Penades, S.Acta Physica Polonica A, 113 (2008) 515-520
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In spite of the diamagnetic behavior exhibited by bulk ZnO and Au, a ferromagnetic-like behavior is induced in nanoparticles of both systems by appropriate surface functionalization. By capping with thiol derivatized molecules, magnetic hysteresis is observed even at room temperature, whereas the magnetization has a very little temperature dependence. Capping induces an alteration of their electronic configuration that depends on the capping molecule, as evidenced by X-ray absorption spectroscopy, that strongly affects their magnetic properties.
Enero, 2008 | DOI: 10.12693/APhysPolA.113.515
Nanotecnología en Superficies y Plasma
"in situ" XPS studies of laser induced surface cleaning and nitridation of Ti
Lahoz, R; Espinos, JP; de la Fuente, GF; Gonzalez-Elipe, ARSurface & Coatings Technology, 202 (2008) 1486-1492
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A titanium foil has been subjected to laser irradiation "in situ" in a pre-chamber of an X-ray photoemission spectrometer under different atmospheres (vacuum, Ar, 02, air, N-2 and H-2). As a result of these treatments, a high amount of the carbon contamination layer was removed and other changes in composition were induced. Nitridation was achieved by laser irradiation under nitrogen. The most effective treatment protocol included an initial cleaning procedure induced by irradiation in vacuum, followed by a second irradiation process performed under nitrogen. Partial nitridation is also observed when irradiating under synthetic air. Lateral and depth analysis of the nitrogen concentration around the laser spot has been also carried out. It is found that the outermost layers present a similar concentration of nitrogen. In addition, the measured nitrogen profile indicates that the amount of nitrogen within the laser spot region is relatively lower than within the immediately surrounding area. Almost no nitrogen remains in the spot area after sputtering for 30 min. A model is proposed to account for the observed titanium surface nitridation processes.
Enero, 2008 | DOI: 10.1016/j.surfcoat.2007.06.061
Química de Superficies y Catálisis
Apatite and Portland/apatite composite cements obtained using a hydrothermal method for retaining heavy metals
Dominguez, MI; Carpena, J; Borschnek, D; Centeno, MA; Odriozola, JA; Rose, JJournal of Hazardous Materials, 150 (2008) 99-108
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Apatite and Portland/apatite composite cements containing steelwork dusts have been prepared using a low temperature hydrothermal method (200° C, 48 h). The produced solids were characterized by means of XRD, IR, and SEM-EDX, and the remaining liquid was analyzed by ICP. The results clearly show the capability of these cements to inertise the heavy metals contained in steelwork dusts, that is Fe, Pb, Mo, Cr, Mn, Ni, and Zn. In the case of apatitic cements, Fe, Mg, Cr, Mn, and Pb coming from steel dust replaced Ca in the divalent cation position of the apatite structure, while Si and Mo replaced P in tetrahedral position. The average crystal size of the apatite-containing dust is smaller than in pure apatite synthesized using the same procedure, which is related to the magnesium content of the dust, since magnesium seems to inhibit the crystal growth. XRD diagrams of composite cements show only peaks corresponding to phases observed in the single cements, and in that no new phases are found. However, EDX analysis reveals the introduction of cations coming from Portland cement into the apatite structure. From the results of water analysis it could be concluded that the capability of retention is higher in composite matrices than in the pure apatite one. In conclusion, the obtained data allow stating that the proposed method, the hydrothermal synthesis of steelwork dust containing cement, is a reliable one for immobilization of toxic residues containing heavy leachable cations.
Enero, 2008 | DOI: 10.1016/j.jhazmat.2007.04.091
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